Sealed type comprssor

ABSTRACT

A sealed type compressor includes a sealed vessel, compression and drive elements disposed in the sealed vessel, an oil pump and an oil supply groove. Upper and lower bearings sandwich the cylinder and piston of the compression element from respective axial sides. The drive element drives the compression element via a crank shaft. The lower bearing has an axially extending bearing portion to support the crankshaft. The oil pump draws up a lubricant into an oil channel extending in a shaft center direction of the crankshaft to provide lubrication to the compression and drive elements. The oil supply groove is provided at a sliding face of the bearing portion, and extends along the crankshaft to supply the lubricant to an outer surface of the crankshaft. The oil supply groove has a first open end side and a second closed end side at a lower end side of the crankshaft.

TECHNICAL FIELD

The present invention relates to a sealed type compressor, moreparticularly, an improvement in the structure of a sealed typecompressor.

BACKGROUND ART

<Overall Arrangement of Rotary Compressor>

An overall arrangement of a rotary compressor will be described withreference to FIG. 6. FIG. 6 is a vertical sectional view representing anoverall arrangement of a rotary compressor. At the lower end side of acasing 1 is arranged a compression element 7 corresponding to inductionpipes 5 a and 5 b for compressing the input working fluid. In addition,a drive element 8 for driving compression element 7 is arrangedthereabove, occupying substantially the entire region of the internalspace. At the internal space defined by a lower lid 4 at the lower endregion of casing 1, an oil reservoir 9 storing a lubricant O is formed.A storage space 10 for storing compressed working fluid is formed atanother space.

<Compression Element 7>

Compression element 7 is configured having a cylinder chamber at anupper stage and at a lower stage, i.e. two cylinder chambers.Compression element 7 includes an upper cylinder 12 a with a cylinderchamber 11 a having a circular transverse cross section, a lowercylinder 12 b with a cylinder chamber 11 b having a circular transversecross section, and a middle plate 18 therebetween. On both upper andlower surfaces of upper cylinder 12 a and lower cylinder 12 b areprovided an upper bearing 13 having a boss-shaped bearing portion 13 aat its center and a lower bearing 14 also having a boss-shaped bearingportion 14 a at its center, fastened by a plurality of bolts 15 to setcylinder chambers 11 a and 11 b at a sealed state.

Upper cylinder 12 a and lower cylinder 12 b are supported at ahorizontal state in casing 1. An outlet 13 c is provided at upperbearing 13. A front muffler 16 is secured to upper bearing 13 aroundbearing portion 13 a so as to form an annular gap with respect tobearing portion 13 a of upper bearing 13. Furthermore, an outlet 14 c isprovided at lower bearing 14. In addition, a rear muffler 17 thatpartitions oil reservoir 9 from the discharge space is secured to lowerbearing 14 around bearing portion 14 a of lower bearing 14.

An upper piston 19 a and a lower piston 19 b are arranged at cylinderchambers 11 a and 11 b of upper cylinder 12 a and lower cylinder 12 b,respectively. Upper and lower pistons 19 a and 19 b are arranged at theouter circumference of eccentric portions 20 a and 20 b of a crankshaft26.

<Drive Element 8>

Drive element 8 includes an electric motor constituted of a stator 24and a rotor 25. Stator 24 is fixedly-supported to an inner wall of amiddle cylindrical body 2 in a casing 1. A rotor 25 is disposedconcentrically with and at the inner side of stator 24 with apredetermined circumferential gap therebetween. The upper half portionof crankshaft 26 is mounted at the inner side of rotor 25 to rotateintegrally about the shaft center. The lower half portion of crankshaft26 is fit-supported rotatably by both bearing portions 13 a and 14 a ofupper bearing 13 and lower bearing 14.

An oil channel 26 a extending along the shaft center direction is formedat crankshaft 26. A centrifugal oil pump 27 is attached at the lower endof crankshaft 26. Oil pump 27 is constantly immersed in lubricant O ofoil reservoir 9 to draw up lubricant O into oil channel 26 a accordingto the rotation of crankshaft 26. The lubricant is supplied through aplurality of lubricant supply holes 26 b provided at crankshaft 26 toeach slidable site of compression element 7 and drive element 8.

The supply of lubricant towards bearing portion 14 a of lower bearing 14will be described hereinafter with reference to FIGS. 7 and 8. FIG. 7 isa perspective view of lower bearing 14, viewed from the bearing portion14 a side. FIG. 8 is a vertical sectional view of lower bearing 14. Asshown in FIG. 7, a communicating groove 14 c is provided at the innercircumferential face of bearing portion 14 a of lower bearing 14,spanning from the upper end to the lower end in parallel with crankshaft26 along the shaft center direction. The lubricant output from lubricantsupply opening 26 b provided at crankshaft 26 runs along the outersurface of crankshaft 26 (F1) via communicating groove 14 c to besupplied to the region between bearing portion 14 a and the sliding faceof crankshaft 26 (F2).

Since communicating groove 14 c has both the upper and lower ends openas shown in FIG. 8, not all the lubricant (F1) output from lubricantsupply hole 26 b is supplied to the region between bearing portion 14 aand the sliding face of crankshaft 26. A portion of the lubricant (F3)is discharged to oil reservoir 9 without being used as the lubricant.

It is to be noted that oil pump 27 draws up an amount of lubricant, aportion that will discharged to oil reservoir 9 without being used forlubrication, in addition to the amount required for lubrication towardsrespective sliding sites, causing futile pump loss. Patent Document 1set forth below can be cited as a document disclosing a rotarycompressor such as that shown in FIG. 4. In addition, Non-PatentDocument 1 can be cited as a document disclosing the art of a rotarycompressor oil supply system.

Patent Document 1: Japanese Patent Laying-Open No. 2004-324652

Non-Patent Document 1: Takahide Ito et al. “Study On Oil Supply Systemfor Rotary Compressors”, Mitsubishi Juko Giho, Mitsubishi HeavyIndustries Ltd. September 1992, Vol. 29, No. 5, pp. 458-462

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

The problem to be solved by the invention arises from the fact that theoil supply groove provided at the lower bearing employed in a sealedtype compressor is a communicating groove with both the upper and lowerends open. Futile pump loss occurs since the oil pump must draw up thelubricant that is merely to be output to the oil reservoir without beingsupplied to the lower bearing even though there is sufficient lubricantto be discharged to the oil reservoir. Thus, the present invention isdirected to solving the above-described problem, and provides a sealedtype compressor allowing improvement in the oil supply capability of theoil pump to suppress occurrence of pump loss by reducing futileinduction of lubricant at the oil pump.

Means for Solving the Problems

A sealed type compressor according to the present invention has acompression element and a drive element accommodated in a sealed vessel,and includes a crankshaft, a piston disposed at an outer circumferenceof an eccentric portion of the crankshaft, a cylinder defining acylinder chamber where the piston is disposed, and an upper bearing anda lower bearing having a bearing portion to support the crankshaftaxially, and sandwiching the cylinder and the piston from respectiveaxial sides of the crankshaft.

The sealed type compressor includes an oil pump provided at a lower endof the crankshaft to draw up a lubricant stored in an oil reservoir atthe lower end portion of the sealed vessel into an oil channel providedextending along a shaft center direction of the crankshaft to providelubrication to each sliding site of the compression element and driveelement, and an oil supply groove provided at a sliding face of thebearing portion of the lower bearing, extending along an axial directionof the crankshaft to supply the lubricant to the outer surface of thecrankshaft.

The oil supply groove has one end side open at an end face of thecylinder side, and the other end side closed at a lower end side of thecrankshaft.

Effects of the Invention

According to the sealed type compressor of the present invention, theoil supply groove provided at the lower bearing is not a communicatinggroove open at the upper and lower ends, and is closed at the lower endside of the crankshaft. As a result, the lubricant supplied to the lowerbearing is entirely applied to the lower bearing without a portion beingdischarged to the oil reservoir.

Thus, by reducing futile induction of lubricant at the oil pump, the oilsupply capability of the oil pump can be improved to suppress occurrenceof pump loss.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of only a lower bearing employed in arotary compressor according to an embodiment of the present invention,viewed from the bearing portion side.

FIG. 2 is a vertical sectional view of a lower bearing employed in arotary compressor according to an embodiment of the present invention.

FIG. 3 represents the oil supply rate to each sliding site when thelower bearing of background art is employed, and the oil supply rate toeach sliding site when the lower bearing of the present embodiment isemployed.

FIG. 4 is a sectional view representing the dimensional relationship ofa lower bearing employed in a rotary compressor according to anembodiment of the present invention.

FIG. 5 represents the relationship of X/L and the bearing temperatureincrease (° C.) of a lower bearing employed in a rotary compressoraccording to an embodiment of the present invention.

FIG. 6 is a vertical sectional view representing an overall arrangementof a rotary compressor according to background art.

FIG. 7 is a perspective view of only a lower bearing employed in arotary compressor according to background art, viewed from the bearingportion side.

FIG. 8 is a vertical sectional view of a lower bearing employed in arotary compressor according to background art.

DESCRIPTION OF THE REFERENCE SIGNS

1 casing; 4 lower lid; 5 a, 5 b induction pipe; 7 compressor element; 8drive element; 9 oil reservoir; 10 storage space; 11 a, 11 b cylinderchamber; 12 a upper cylinder; 12 b lower cylinder; 13 upper bearing; 13a bearing portion; 13 c, 14 c outlet; 14A lower bearing; 14 a bearingportion; 14 b oil supply groove; 14 c communicating groove; 15 bolt; 16front muffler; 17 rear muffler; 18 middle plate; 19 a upper piston; 19 blower piston; 24 stator; 25 rotor; 26 a oil channel; 26 b lubricantsupply hole; 27 oil pump; O lubricant.

BEST MODES FOR CARRYING OUT THE INVENTION

Each of the embodiments of a sealed type compressor according to thepresent invention will be described hereinafter with reference to thedrawings. As an example of a sealed type compressor of the presentembodiment, an application of the present invention to the rotarycompressor set forth above in the background art will be described.

The rotary compressor of the present embodiment has the same basicarrangement as the rotary compressor with a cylinder chamber at an upperstage and at a lower stage, i.e. two cylinder chambers, described withreference to FIG. 6. A compression element 7 and a drive element 8 areaccommodated in a casing 1 that is a sealed vessel. The rotarycompressor includes a crankshaft 26, an upper piston 19 a and a lowerpiston 19 b arranged at the outer circumference of eccentric portions 20a and 20 b of crankshaft 26, an upper cylinder 12 a and a lower cylinder12 b defining cylinder chambers 11 a and 11 b where upper piston 19 aand lower piston 19 b are disposed, and bearing portions 13 a and 14 ato axial-support crankshaft 26.

There are further provided an upper bearing 13 and a lower bearing 14sandwiching upper cylinder 12 a, upper piston 19 a, lower cylinder 12 band lower piston 19 b from respective axial sides of crankshaft 26.

In addition, at the lower end of crankshaft 26 is provided an oil pump27 to draw up a lubricant O stored in an oil reservoir 9 at the lowerend portion of casing 1 into an oil channel 26 a provided so as toextend along the shaft center direction of crankshaft 26 to, providelubrication to each sliding site of compression element 7 and driveelement 8, according to the rotation of crankshaft 26.

In the following description, elements identical to or corresponding tothose of the rotary compressor described with reference to FIG. 6 havethe same reference characters allotted, and description thereof will notbe repeated. Only the characteristic features of the present inventionwill be described in detail hereinafter.

Referring to FIGS. 1 and 2, the characteristic portion of the rotarycompressor of the present embodiment will be described. FIG. 1 is aperspective view of only lower bearing 14A employed in the rotarycompressor of the present embodiment, viewed from the bearing portion 14a side. FIG. 2 is a vertical sectional view of lower bearing 14A.

As shown in FIG. 1, an oil supply groove 14 b is provided at the innercircumferential face of bearing portion 14 a of lower bearing 14A. Oilsupply groove 14 b has one end side open at the end face of the cylinder12 b side (refer to FIG. 6). The other end side of oil supply groove 14b extends to a region partway of bearing portion 14 a at the lower endside of crankshaft 26.

The lubricant (F1) discharged from lubricant supply opening 26 bprovided at crankshaft 26 (refer to FIG. 6) runs along the outer surfaceof crankshaft 26 via oil supply groove 14 b to be supplied to the regionbetween bearing portion 14 a and the sliding face of crankshaft 26 (F2).

As shown in FIG. 2, oil supply groove 14 b is not a communicating grooveopen at the lower end, and extends to a region only as far as partway ofbearing portion. 14 a at the lower end side of crankshaft 26. Since oilsupply groove 14 b takes a closed state at the lower end side ofcrankshaft 26, the lubricant supplied to lower bearing 14A is entirelyapplied to lower bearing 14A without a portion being discharged to oilreservoir 9 (refer to FIG. 6). FIG. 1 represents a configuration inwhich oil supply groove 14 b extends to a region only as far as partwayof bearing portion 14 a at the lower end side of crankshaft 26. In thecase where the groove is provided extending from the upper end to thelower end of crankshaft 26, likewise of communicating groove 14 c shownin FIG. 7, a structure of closing the lower end side of the oil supplygroove can be adapted by providing another member such as a plate memberat the lower end of the groove.

FIG. 3 represents the oil supply rate (cc/min) of the lubricant to eachsliding site corresponding to the case where lower bearing 14 of thebackground art shown in FIG. 8 is employed, and the oil supply rate(cc/min) to each sliding site corresponding to the case where lowerbearing 14A of the present embodiment is employed. The oil supply rate(cc/min) of the lubricant supplied to the upper bearing (A1), upperpiston 19 a (A2), and lower piston 19 b (A3) does not vary between thebackground art and the present embodiment.

However the oil supply rate (cc/min) of lubricant to the lower bearing(A4) is greatly reduced in the present embodiment, as compared to thatof the background art. This is because the lubricant supplied to lowerbearing 14A of the present embodiment is entirely applied to lowerbearing 14 without being partially discharged to oil reservoir 9 (referto FIG. 6), as described before, avoiding unnecessary drawing up oflubricant by oil pump 27.

The effect on the bearing performance when oil supply groove 14 b isclosed at the lower end side of bearing portion 14 a will be studiedfrom the standpoint of <bearing friction loss> and <cooling performanceof bearing>.

<Bearing Friction Loss>

The most critical factor in the issue of the oil supply rate involved inthe reliability of a bearing is the cooling performance. It is possibleto appraise the cooling performance by estimating how much the oiltemperature rises by the generated bearing friction loss. The bearingfriction loss W can be expressed by equation 1 set forth below, where Lis the overall bearing length, r the bearing radius, μ the oilviscosity, u the sliding rate, C the clearance, and δ the oil filmclearance. Assuming that overall bearing length L, bearing radius r, oilviscosity μ and sliding rate u are constants in equation 1, bearingfriction loss W will rapidly increase when the oil film clearance δapproaches zero.

W=[2πLrμu ²]÷[C(1−δ²)^(1/2)]  (1)

(where λ=1−(δ/C))

<Cooling Performance of Bearing>

In the case where it is assumed that the oil supply rate to the bearingvaries linearly when the length of the oil supply groove is shortened,and that the oil film clearance in such a case also varies linearly inproportion to the oil supply rate, a shorter length of the oil supplygroove causes reduction in the oil supply rate, which in turn reducesthe oil film clearance to increase the bearing friction loss. It is tobe noted that the bearing friction loss tends to increase suddenly whenthe oil film clearance becomes small, as indicated by equation 1 setforth above. Therefore, when the oil film clearance becomes small, thetemperature of the bearing rises significantly since cooling is effectedwith a smaller amount of lubricant corresponding to the greater bearingfriction loss.

The relationship between the ratio (X/L) of the length of the oil supplygroove (X) to the entire length of the bearing (L) and the bearingtemperature increase will be described with reference to FIGS. 4 and 5.FIG. 4 is a sectional view representing the dimensional relationship oflower bearing 14A. FIG. 5 represents the relationship between X/L andthe bearing temperature increase (° C.). As shown in FIG. 5, the bearingtemperature is maintained below approximately 20 degrees when the X/L isfrom 0.4 to 1. The bearing temperature is also below approximately 40degrees when the X/L is from 0.2 to 0.4. However, when the X/L becomeslower than 0.2, the oil film clearance becomes small to cause increaseof the bearing friction loss. As a result, the cooling performance isgreatly degraded. It is therefore desirable that the X/L is in the rangefrom 0.2 to 0.8, preferably from 0.6 to 0.8.

Although the embodiment has been described based on the case where thepresent invention is applied to a rotary compressor having a cylinder atan upper stage and at a lower stage, i.e. two cylinders, the presentinvention is also applicable to a rotary compressor having a cylinder atone stage. Moreover, the structure based on the present invention iswidely applicable, not only to rotary compressors, but to other sealedtype compressors having a similar compression element structure.

It should be understood that the embodiments disclosed herein areillustrative and non-restrictive in every respect. The scope of thepresent invention is defined by the appended claims, and all changesthat fall within the limits and bounds of the claims, or equivalencethereof are intended to be embraced by the claims.

1. A sealed type compressor having a compression element (7) and a driveelement (8) accommodated in a sealed vessel (1), the sealed typecompressor including a crankshaft (26), a piston (19 a, 19 b) disposedat an outer circumference of an eccentric portion (20 a, 20 b) of saidcrankshaft (26), a cylinder (12 a, 12 b) defining a cylinder chamber (11a, 11 b) where said piston (19 a, 19 b) is disposed, and an upperbearing (13) and a lower bearing (14) having a bearing portion (13 a, 13b) to support said crankshaft axially, and sandwiching said cylinder (12a, 12 b) and said piston (19 a, 19 b) from respective axial sides ofsaid crankshaft (26), said sealed type compressor comprising: an oilpump (27) provided at a lower end of said crankshaft (26) to draw up alubricant (O) stored in an oil reservoir (9) at a lower end portion ofsaid sealed vessel (1) into an oil channel (26 a) provided extending ina shaft center direction of said crankshaft (26) to provide lubricationat each sliding site of the compression element (7) and drive element(8), according to rotation of said crankshaft (26), and an oil supplygroove (14 b) provided at a sliding face of said bearing portion (14 a)of said lower bearing (14), extending along an axial direction of saidcrankshaft (26) to supply the lubricant to an outer surface of saidcrankshaft (26), said oil supply groove (14b) having one end side openat an end plane of said cylinder (12 b) side and an other end side ofsaid oil supply groove (14 b) closed at a lower end side of saidcrankshaft (26).
 2. The sealed type compressor according to claim 1,wherein the other end side of said oil supply groove (14 b) extends to aregion partway of said bearing portion (14 a).
 3. The sealed typecompressor according to claim 1, wherein a value of X/L is set in arange from 0.2 to 1.0, where X is a length of said oil supply groove (14b) and L is an overall bearing length L of said bearing portion (14 a).